The present invention relates to an auxiliary optical unit attachable to an optical device for optional use with such device. The invention is particularly useful when embodied as an add-on device to a telescopic gun sight, such as a night vision or day vision gun sight, and is therefore described below with respect to such application.
Rifles and similar guns are frequently aimed at long distances by using a telescopic gun sight. Such sights include horizontal and vertical cross-hairs or reticles to facilitate aiming the rifle towards the target. The rifle angle above horizontal must be increased according to the distance to the target to compensate for the vertical drop by the projectile during its flight from the rifle to the target. Therefore, gun sights frequently include a range finder, such as a laser range finder, for measuring and displaying the range to the object.
Telescopic gun sights are usually designed to produce a predetermined magnification of the sighted target. If the telescopic gun sight is also to be used at night, it would also include a light-intensifier tube to enable night vision.
It will be appreciated that incorporating a range finder in the telescopic sight increases its size and weight. It will also be appreciated that increasing the magnification of the sight decreases its field of view. Both of the above can significantly affect the efficient use of telescopic gun sights, as well as of other optical devices such as cameras, microscopes, etc.
An object of the present invention is to provide an optical system particularly, but not exclusively, useful with respect to telescopic gun sights for avoiding one or both of the above drawbacks.
According to a broad aspect of the present invention, there is provided an auxiliary optical unit attachable to an optical device for optional use therewith, the auxiliary optical unit comprising: (a) an afocal teleconverter lens system having a predetermined magnification; (b) a laser range finder system for measuring and displaying the range to viewed object; and (c) a beam splitter located within the auxiliary optical unit such that when the auxiliary optical unit is attached to the optical device, both the displayed range and the object are concurrently viewable by the optical device.
Afocal teleconverter lens systems are commonly used in photography. A teleconverter is an auxiliary lens fitted between an interchangeable lens of the cameras and the camera body or a telescope objective lens in order to change the focal length of the interchangeable lens. The interchangeable lens is known in this case as the main lens. When a teleconverter is used, the F number is increased by the same proportion as the amount the teleconverter multiplies the focal length. For example, if the focal length is doubled, the aperture is smaller by two stops; if the focal length is multiplied by 1.4, the aperture is smaller by one stop. Such a system provides a virtual image of parallel light rays which can be photographed afocally with a digital camera. Most of the lower power (xcx9c3xc3x97) commercial teleconverters are actually small Galilean telescopes consisting of a positive achromat lens and a concave rear lens.
As will be described more particularly below, such an auxiliary optical unit may be embodied in a relatively small, lightweight, compact unit quickly attachable and detachable to the optical device. For example, where the optical device is a telescopic gun sight, the gun sight may be used alone for relatively short ranges and with relatively low magnification, thereby providing a relatively wide field-of-view, as well as a compact and light-weight telescopic sight. However, when the telescopic sight is to be used at relatively larger ranges, of which the user should be informed to properly aim the rifle, or when larger magnification is desired, the auxiliary optical unit may be quickly attached to the telescopic gun sight to provide a measurement and display of the range, as well as a magnification, of the target imaged by the gun sight. When the auxiliary optical unit is no longer needed, it may be quickly detached to enable the telescopic gun sight again to be used without the drawbacks of increased size and weight and decreased field of view.
According to further features in the preferred embodiments of the invention described below, the afocal teleconverter lens system includes: a teleconverter front lens oriented to view a desired object, and a teleconverter rear lens oriented to be in alignment with the optical axis of the optical device when attached thereto; the beam splitter is located between the teleconverter front lens and the teleconverter rear lens.
According to still further features in the described preferred embodiments, the laser range finder system includes: (i) a laser transmitter for generating and transmitting a laser beam; (ii) a laser beam transmitter lens; (iii) a laser receiver for receiving the laser beam and for measuring the range; and (iv) a display module for displaying the measured range.
Two embodiments of the invention are described below for purposes of example. In one described preferred embodiment, the auxiliary optical unit includes a laser beam receiver lens for receiving the laser beam after reflection from the object. In a second described preferred embodiment, the laser beam is received via the teleconverter front lens and is reflected by the beam splitter towards the laser receiver module.
As indicated above, while the invention is particularly useful with telescopic gun sights, it may also be used with other optical devices, such as cameras, microscopes, monoculars, binoculars, etc.
Further features and advantages of the invention will be apparent from the description below.